The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIG. 1, a functional block diagram of a hybrid powertrain of a vehicle is presented. The hybrid powertrain includes an engine 102, a motor generator unit (MGU) 104, an inverter 106, a hybrid battery 108, and an accessory power module (APM) 110. The APM 110 is typically a DC to DC converter that converts power from the hybrid battery 108 to a standard vehicle voltage, such as a nominal 12V voltage for 12V battery 114 and 12V vehicle loads 116. By using the APM 110, the 12V battery 114 and the 12V vehicle loads 116 do not need to be redesigned to work with the higher voltage of the hybrid battery 108.
The power conversion efficiency of the APM 110 is typically greater than 85%. The engine 102 is coupled to a transmission (not shown) in the standard manner. The transmission is coupled to the vehicle's wheels. Positive torque from the engine 102 propels the vehicle forward via the transmission and wheels. When the vehicle decelerates, the torque path is reversed and the wheels backdrive the transmission, which in turn backdrives the engine 102.
The inverter 106 converts power between the MGU 104, which may be a 40V 3-phase AC electrical machine, and the DC voltage of the hybrid battery 108, which may be 40V. The mode of operation of the MGU 104, either motor or generator, is configured by commands to the inverter 106.
The engine 102 and the MGU 104 may be coupled via a belt 120 that encircles pulleys 122 and 124 of the engine 102 and the MGU 104, respectively. The MGU 104 is selectively controlled by the inverter 106 to either produce positive torque (motor operation that consumes electric power) or negative torque (generator operation that creates electric power). The combined torque of the engine 102 and the MGU 104 affect the vehicle's speed and acceleration.
When more propulsion torque is desired than the engine 102 is currently producing, the MGU 104 can be used as a motor to provide additional positive torque. When the MGU 104 produces positive torque, power for both the MGU 104 and the APM 110 is sourced from the hybrid battery 108.
At times when the engine 102 is producing more torque than is required, the MGU 104 can function as a generator, providing DC power at the output of the inverter 106. In addition, during regenerative braking, the MGU 104 also functions as a generator, slowing the vehicle while providing electrical power. When the MGU 104 produces negative torque, the electrical power is directed to both the APM 110 and the hybrid battery 108 from the inverter 106. Power is first consumed by the APM 110, while additional power in excess of the load from the APM 110 is stored in the hybrid battery 108.